Feasible numerical method for analysis of offshore pipeline in installation     

《Applied Ocean Research》2019

Feasible numerical method for a structural analysis of a pipeline configuration during the installation process is presented. The method considers the whole pipeline, which is partially suspended and partially laid-on a seabed, as a single continuous segment, and is valid for a complete range of laying angles between 0°–90°, i.e., valid for both S-lay and J-lay configurations. The method accounts for a pipeline–seabed interaction and the pipeline is modeled by means of nonlinear large deformation beam theory. The numerical solution is carried out in an incremental-iterative manner by following the actual pipeline installation process, and thus allowing efficient treatment of pipeline-seabed interaction circumventing the further complexities with contact detection. At each increment, the length of the pipeline is increased and new sequential equilibrium configuration is assessed by direct minimization of a total potential energy approximated as a Riemann sum, which yields algebraic system of nonlinear finite difference equations that is further solved by iterations with Newton-Raphson technique. The simplicity, flexibility and robustness of the proposed method allow to enhance the efficiency of engineering calculations and design. Accounting for a bending stiffness in a suspended part allows analyzing variations in laying angle and lay tension independently. The method convergence is validated and compared with Abaqus. The results are in an excellent agreement. Moreover, the comparison with Abaqus shows that for the selected parameters the assumption that the pipeline is inextensible and unshearable is very reasonable. Representative parametric study is conducted to demonstrate the feasibility of the method. Parametric study considers the effects of laying angle (0°–90°), lay tension, laying water depth (up to 3000 m) and seabed stiffness.  相似文献   

线纹海马Hippocampus erectus的tlr21基因结构及其对CpG-ODN的应答特征     

张媛  秦耿  张博  林强 《热带海洋学报》2019,38(1):67-75

作为先天性免疫反应中重要的模式识别受体之一, TLR(toll-like receptor)基因家族介导的先天性免疫是脊椎动物抵御病原微生物的重要防线。研究分析了线纹海马Hippocampus erectus tlr21基因的序列特征, 并基于抗原注射实验探讨了海马tlr21的免疫功能。线纹海马tlr21基因的开放阅读框长度为2946bp, 编码981个氨基酸, 预测其编码蛋白相对分子量为246.98kDa, 理论等电点为4.78。tlr21编码蛋白主要包含1个信号肽和3个功能结构域: 胞外区具有14个富含亮氨酸重复序列的结构域(LRR), 跨膜区具有富含半胱氨酸的结构域, 胞内区则具有TIR结构域。同源性比较和系统进化分析表明, 线纹海马tlr21基因与虎尾海马Hippocampus comes tlr21基因的同源性最高, 其次与斜带石斑鱼Epinephelus coioides、牙鲆Paralichthys olivaceus、大菱鲆Scophthalmus maximus和红鳍东方鲀Takifugu rubripes的tlr21基因聚为一枝。tlr21基因在线纹海马的脑、鳃、肝、肠、肾、性腺、肌肉和育儿袋各组织均有分布, 肾脏中表达量最高。抗原注射实验结果发现, 线纹海马Tlr21对不同类型CpG寡脱氧核苷酸(CpG-ODNs)的识别能力存在差异, 其中, CpG-2007和CpG-HC4040对海马肾脏tlr21的mRNA表达量具有显著的促进作用(P<0.05)。研究表明, 线纹海马Tlr21能够通过识别含CpG序列的DNA发挥免疫识别作用, 研究结果将有助于系统认识海马免疫系统中TLR家族基因的功能特征, 为建立海马病害防治策略提供理论依据。  相似文献   

风云三号C星微波成像仪升降轨偏差问题分析及订正     

张淼  陆其峰  谷松岩  胡秀清  武胜利 《遥感学报》2019,23(5):841-849

风云三号(FY-3)的微波成像仪(MWRI)能够全天候获取全球大气水汽含量、云雨参数及海面温度等的空间分布,并可为数值天气预报提供初始场信息进而提高天气预报的准确性。但FY-3C MWRI O-B(O是卫星观测亮温,B是数值天气预报模式模拟亮温)偏差结果存在较大升降轨差异,严重制约了遥感信息的正确提取以及在数值天气预报模式中的业务同化应用。本文通过分析定标方程各参数:定标黑体物理温度、热反射镜背瓣亮温、热反射镜物理温度、冷空反射镜物理温度、接收通道温度、黑体观测计数值、冷空观测计数值、定标斜率、定标截距,并对定标方程各项进行敏感性分析,找出了引起MWRI升降轨偏差的主要原因是热反射镜的发射率异常增大引起的。经过不断调整MWRI的热反射镜发射率,使升轨O-B与降轨O-B的概率分布逐渐重合,初步估算了热反射镜发射率。本文的订正方法可指导未来仪器的发展,并为直接同化MWRI辐射数据提供了条件。  相似文献   

复杂环境下高分二号遥感影像的城市地表水体提取   总被引：1，自引：0，他引：1  

洪亮  黄雅君  杨昆  彭双云  许泉立 《遥感学报》2019,23(5):871-882

水体指数可以抑制背景噪声和提高地表水体的可分性,已经广泛用于地表水体提取。传统FCM聚类算法考虑了地物的不确定性,但没有顾及地物的邻域空间信息,对背景异质性比较敏感。针对传统FCM聚类算法的不足,提出一种可变邻域的区域FCM聚类算法。由于复杂环境下高分二号(GF-2)遥感影像的城市地表水体具有复杂异质背景和不确定性的特点,本文利用水体指数和区域FCM聚类算法的优点,提出一种整合水体指数和区域FCM的城市地表水体自动提取算法,该算法主要步骤包括:(1)去除影像阴影后计算归一化差分水体指数NDWI(Normalized Difference Water Index);(2)区域FCM聚类算法;(3)整合水体指数和区域FCM聚类的城市地表水体自动提取算法。最后采用两景GF-2高分辨率遥感影像(广州和武汉)进行实验,验证了该算法的有效性,并与经典地表水体提取算法进行对比分析。实验结果表明:该算法具有较高的水体提取精度,城市地表水体边界既具有较好的区域完整性又保持了局部细节,同时对城市地表水体复杂背景噪声具有较好的抑制作用,有效减少传统FCM聚类算法的"胡椒盐"现象。  相似文献   

基于卡尔曼滤波方法的BDS动态伪距差分定位算法研究          下载免费PDF全文

孙茂军  李霞  赵利江 《全球定位系统》2019,44(3):69-73

针对北斗卫星导航系统(BDS)最小二乘伪距差分方法定位精度及稳定性不足的问题,提出了一种基于卡尔曼滤波方法的伪距差分算法,并进行了静态以及人行慢动态两种条件下的实验.对实测数据结果的处理分析表明,卡尔曼滤波方法在静态条件下,东、北、高三个方向精度分别提升55%、23%、48%.在动态条件下,东、北、高三个方向精度分别提升71%、49%、33%.  相似文献   

Storm surge simulation along the Meghna estuarine area: an alternative approach   总被引：1，自引：1，他引：0  

PAUL Gour Chandr  SENTHILKUMAR Sukumar  PRIA Rana 《海洋学报(英文版)》2018,37(1):40-49

In this study, numerical prediction of surges associated with a storm was made through the method of lines (MOL) in coordination with the newly proposed RKARMS (4, 4) method for the meghna estuarine region, along the coast of Bangladesh. For this purpose, the vertically integrated shallow water equations (SWEs) in Cartesian coordinates were firstly transformed into ordinary differential equations (ODEs) of initial valued, which were then soloved using the new RKARMS (4, 4) method. Nested grid technique was employed for resolving the complexities of the region of interest with minimum cost. Fresh water discharge through the lower Meghna River was taken into account along the north east corner of the innermost child scheme. Numerical experiments were performed with the severe cyclone on April 1991 that crossed the coast over the study area. Simulated results by the study were found to be in good agreement with some reported data and were found to compare well with the results obtained by the MOL in addition with the classical 4th order Runge-Kutta (RK (4, 4)) method and the standard finite difference method (FDM).  相似文献   

中国出口贸易韧性空间差异性研究   总被引：3，自引：1，他引：2  

贺灿飞  夏昕鸣  黎明 《地理科学进展》2019,38(10):1558-1570

金融危机时期,中国区域出口韧性表现出危机第一阶段(2008—2009年)的抵抗力、危机第二阶段(2009—2011年)的恢复力、产品结构转换提升力。论文构建了区域-产品层面的区域出口贸易韧性指标,通过区域出口贸易额、产品结构等不同层面刻画了金融危机后各区域抵抗力、恢复力的空间差异。实证研究表明：相关多样化产业结构不仅在短期可以增强区域产品的抵抗力,在长期还可以提高区域产品的恢复力并且助推区域产品实现结构升级;应急型税收政策短期内一定程度上可以有效缓解危机冲击,但其影响范围及作用时间均是有限的;外企出口占比高的区域产品对区域产品结构升级影响不明显,但加工贸易方式推动了区域产品在危机中的结构升级。  相似文献   

美国ASTM规范下标贯成果在尼罗河地质勘察中的应用     

段伟强 《地下水》2020,(1):131-133

标准贯入试验是现场测定土体工程性质的重要原位试验,是现场快速判定土体密实度的重要依据,具有及时、可靠、经济等特点,在地质勘察中被广泛的应用。本文通过介绍标准贯入试验的基本原理和设备,比较了英国规范、美国ASTM规范和我国岩土工程勘察规范之间标准贯入试验的差异,介绍了标准贯入试验所适用的经验公式,结合在美国ASTM规范指导下具体的工程实践结果,应用标准贯入试验的结果分析了苏丹国尼罗河Dagash流域内的土体工程性质,对比钻探所得土样和袖珍贯入测力计试验结果,验证了标贯结果的正确性。  相似文献   

Identification of failure slip surfaces for landslide risk assessment using smoothed particle hydrodynamics     

Liang Li 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(2):91-111

ABSTRACT

Location of failure slip surfaces plays a critical role in landslide risk assessment and mitigation, particularly for unstable slopes, because it is a key input to design of stabilisation measures for unstable slopes and it determines the volume of the sliding soil mass (i.e. landslide consequence). The failure slip surfaces in the numerical analysis (e.g. finite element/different method, FEM/FDM) are often identified using shear strength reduction (SSR) method. A careful examination of FEM results showed that, although the SSR method performs well for stable slopes, it might provide misleading results for unstable slopes. To properly locate failure slip surfaces for unstable slopes, this paper presents a particle-based numerical method called smoothed particle hydrodynamics (SPH), which is mesh-free, immune to the mesh distortion problem in FEM/FDM, and able to directly simulate large deformation of soils that occurs during landslides. A series of slope stability analyses is performed using an in-house SPH programme. Failure slip surfaces are properly identified by SPH for both stable and unstable slopes. Furthermore, because SPH provides a spatial distribution of the post-landslide large displacement of soils, the failure slip surfaces can be identified conveniently using soil displacement. A displacement-based criterion is proposed to locate the failure slip surfaces.  相似文献   

基于POI数据的大型零售商业设施空间布局与业态差异——以广州市为例   总被引：1，自引：0，他引：1  

周丽娜  李立勋 《热带地理》2020,40(1):88-100

以广州市为例,基于大型零售商业设施POI（Point of Interest）数据,运用空间计量分析方法,对大型零售商业设施总体及不同业态的空间分布及其影响因素进行了探究。结果表明：总体上,大型零售商业设施空间分布呈现出由内向外扩散的多中心圈层式结构,沿交通干道生长和连片蔓延趋势明显,中心城区设施临近轨道交通分布指向性突出。不同业态分布差异明显,大型购物中心和商场主要分布在中心城区及外围城区次中心,大型综合超市由中心城区内部向边缘区域扩散趋势明显,大型专业店主要分布在中心城区的边缘区域。影响因素方面,人口、经济和租金因素对其总体分布影响显著为正。不同业态所受影响因素有所不同,除人口等传统影响因素外,与生活中心、产业园或专业市场的临近性也会分别对大型综合超市和大型专业店的空间分布造成显著影响。  相似文献